This invention relates generally to a treatment of water used in recirculating cooling water systems and more particularly to a water treatment composition which effectively controls corrosion and scale formation, which does not rely in any way upon chromate and which will not release orthophosphate into the environment.
Corrosion occurs when metals are oxidized to their respective ions or insoluble salts. For example, corrosion of metallic iron can involve conversion to soluble iron in a +2 or +3 oxidation state or to formation of insoluble iron oxides and hydroxides. Metal loss from the solubilization of the iron causes the structural integrity of the system to deteriorate over time. Leakage between the water system and process streams can ultimately occur. Also, corrosion contributes to the formation of insoluble salts and the resultant buildup of deposits which impede heat transfer and fluid flow.
Chromate has traditionally been an extremely effective and widely used corrosion inhibitor. During recent years, however, the use of chromate has come under increasing scrutiny due to environmental concerns. In light of this, it is most desirable to develop chromate-free, environmentally acceptable corrosion inhibitors.
Similarly, orthophosphate has traditionally been used as a scale inhibitor. The release of free orthophosphate into water systems has come under increasing scrutiny also due to environmental concerns. It is therefore also desirable to develop environmentally acceptable orthophosphate-free scale inhibitors.